A doctor sent me to a neurologist for examination. The neurologist examined me and sent my doctor a report that said there is a strong possibility I have Chronic Fatigue Syndrome. But my doctor never told me this. He never even mentioned CFS to me. And I didn't find out about the report until a year later when I asked for copies of my records and read them.
More recently, a doctor told me my blood work was normal. When I looked at copies of my tests I noticed that some of my levels were ten times higher than the maximum for normal range. When I asked my doctor about this, he said that they are out of range, but it doesn't really tell us anything.
Okay, so they don't tell him anything. But they might tell another doctor something. And if I hadn't found out that my tests were well out of range I would not know to seek a second opinion.
There is another reason for having copies of your medical records at home. It makes it a lot easier when you start with a new doctor who wants to see your other medical records. You can make copies of these and take them in. Or some medical offices will copy them for you.
Update: I got a printer that also copies, scans, and faxes. So now a doctor can fax me lab results and I get them right away. I can also fax them to other doctors of mine who need to see them. Then I make a photocopy, put the original in my file and a copy in my med bag. This way I have a copy on hand if I need to show to a doctor. This includes doctors who already have the report, because sometimes they can't find it. Also, I can use the fax to communicate with pharmacy, get forms I have to fill out for appointments, etc. Or, if I receive a paper copy of a form, I can scan it into my computer, and then type to fill it out. I need this because sometimes I have trouble writing.